Jet engines generally are comprised of several basic components. A compressor provides compressed air to a burner, where the air is mixed with fuel and the resulting mixture is combusted. The heated combustion product is expanded through a turbine to power the compressor, and is then exhausted out the nozzle of the jet.
In order to initiate this process, it is usually necessary to begin rotation of the turbine prior to ignition of the burner, so that the flow from the burner does not have to overcome the resistance of a stationary turbine. Two events are therefore required: initiation of turbine rotation, and ignition of the burner. Turbine rotation is normally initiated by using a pyrotechnic starter cartridge which, when ignited, generates a flow of gas that impinges on either the turbine or compressor to get the system turning to its idle speed. Once idle speed has been attained, prior art systems have employed an additional pyrotechnic device to initiate the operation of the burner. This second pyrotechnic device usually must provide a relatively lengthy pyrotechnic event (from 2 to 8 seconds) to ensure burner ignition. A spark or similar ignition event of short duration is usually insufficient.
Because burner ignition should occur when the turbine rotation reaches idle speed, the two pyrotechnic events must be coordinated. In prior art devices employing two separate pyrotechnic elements, electronic pulses coordinated by a logic system are used to begin each pyrotechnic event. However, the use of two independent devices, and a complicated electronic logic system for sequencing their ignition, makes the overall system complex and prone to malfunction.